1. Field of the Invention
The present invention is directed to a high-power transformer for clocked power supplies comprising at least one primary winding and at least one secondary winding whose respective turns are fashioned as a stranded conductor which, in turn, composed of wire-shaped individual conductors which are provided with an electrically-insulating surface and which are twisted or woven with one another.
2. Description of the Prior Art
Winding conductors for such transformers are known from the European patent application EP-A No. 0133220 and from the French Pat. No. 1198126, both of which are incorporated herein by this reference.
Designs and constructions of standard transformers do not present a person skilled in the art with any difficulties either in theory or in practice. In some applications, however, such as utilization in clocked power supplies having a high output power and high clock frequency, a number of extreme requirements are made of a transformer, this making the realization thereof significantly more difficult.
The requirement for high output current is initially countered with a secondary winding of thick copper bands. In addition to the difficulties in manufacture, however, these transformers were too large and too heavy. When the frequency was then increased in order to save iron in the transformer core, then the skin effect appeared, this causing the charge carriers to be displaced into the edge zone of a conductor. Despite solid copper bands, an increase in the internal resistance of the windings and, therefore, an increased transmission loss then had to be accepted. In order to overcome this disadvantage, the German Pat. No. 32 05 650, fully incorporated herein by this reference, discloses that the thick and solid copper band of a secondary winding be replaced by a plurality of thinner bands insulated from one another and connected to diodes which have their outputs connected together whereby the current is distributed to the diodes.
The efficiency of a transformer constructed in accordance with the above principal decreases with increasing current strength and frequency.